Why is Woocommerce restrict coupon by email_restrictions not working?

Question

I have updated my current coupon to these values

  "amount": "12",
  "individual_use": true,
  "exclude_sale_items": false,
  "minimum_amount": "0.00",
  "email_restrictions": [
      "[email protected]"
  ],
  "usage_limit_per_user": 3

}

but I can post the data with any email id and still get discounted values as per coupon

as you can see from a small snippet of response on success, there is a dicount of 1.32 for email "[email protected]"

{
    "id": 1876,
    "parent_id": 0,
    "status": "processing",
    "currency": "SGD",
    "version": "8.5.1",
    "prices_include_tax": false,
    "date_created": "2024-02-03T08:27:38",
    "date_modified": "2024-02-03T08:27:39",
    "discount_total": "1.32",
    "discount_tax": "0.00",
    "shipping_total": "10.00",
    "cart_tax": "0.00",
    "total": "19.68",
    "billing": {
        "country": "US",
        "email": "[email protected]"
}